Technological aspects of producing gradient planar waveguides for LPWG structures

This paper presents the technological aspect of producing gradient planar waveguides for Long Period Grating Waveguide structures (LPWG). Such waveguides are produced by the Ag+<-> Na+ ion exchange method in Pyrex glass. By a sequence of ion exchange technological processes the refractive profiles of waveguides (multimode area) can be produced in this glass, so that the chosen corrugation period allows the resonant coupling of power conducted in the TE0 fundamental mode to the modes of higher order. On the basis of the determined temperature dependences of diffusion coefficients of exchanged ions the conditions of preliminary diffusion, heating and secondary diffusion (ultimately giving the required refractive index profile of the waveguide) have been determined. The technological processes mentioned above have been realized. After each of these processes the measurements of effective refractive indices of modes have been carried out. A comparison of the values and of the theoretical results has been made as well.